Related papers: The r-Process and Chronometers
The early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find.…
Elemental abundances of the most metal-poor stars reflect the conditions in the early Galaxy and the properties of the first stars. We present a spectroscopic follow-up of two ultra metal-poor stars ([Fe/H]<-4.0) identified by the survey…
We report detailed analysis of high-resolution spectra of nine high velocity metal-rich dwarfs in the solar neighborhood. The stars are super metal-rich and 5 of them have [Fe/H]>=+0.4, making them the most metal-rich stars currently known.…
We report on the first high-resolution spectroscopic analysis of HE0020-1741, a bright (V=12.9), ultra metal-poor ([Fe/H] = -4.1), carbon-enhanced ([C/Fe] = +1.7) star selected from the Hamburg/ESO Survey. This star exhibits low abundances…
We present an analysis of high-resolution Keck/HIRES spectroscopic observations of J0815+4729, an extremely carbon-enhanced, iron-poor dwarf star. These high-quality data allow us to derive a metallicity of [Fe/H]$=-5.49{\pm}0.14$ from the…
We present atmospheric parameters and abundances for chemical elements from carbon to barium in metal-poor stars in Segue 1 (seven stars), Coma Berenices (three stars), and Triangulum II (one star) ultra-faint dwarf galaxies (UFDs). The…
We report on the first high spectral resolution analysis of extremely metal-poor halo stars from the Hamburg/ESO objective-prism survey (HES). The spectra were obtained with UVES at VLT-UT2. The two stars under investigation (\object {HE…
We performed detailed chemical abundance analysis of the extremely metal-poor ([Ar/H]-2) halo planetary nebula H4-1 based on the multi-wavelength spectra from Subaru/HDS, GALEX, SDSS, and Spitzer/IRS and determined the abundances of 10…
We present a new abundance analysis of HD 55496, previously known as a metal-poor barium star. We found that HD 55496 has a metallicity [Fe/H] $=-1.55$ and is s-process enriched. We find that HD 55496 presents four chemical peculiarities:…
We present a detailed abundance analysis based on high resolution and high signal-to-noise spectra of eight extremely metal poor (EMP) stars with [Fe/H] < -3.5$ dex, four of which are new. Only stars with 4900 < Teff< 5650 K are included.…
We present new HST optical imagery as well as new UV and IR spectroscopic data obtained with the Hubble and Spitzer Space Telescopes, respectively, of the halo planetary nebula DdDm-1. For the first time we present a resolved image of this…
Abundances of five elements, Na, Mg, Al, Si, and Sr, are investigated for 44 very metal-poor stars (-4.0 < [Fe/H] < -1.5) in the Galactic halo system based on an Local Thermodinamic Equilibrium (LTE) analysis of high-resolution…
We present the first comprehensive abundance study of the massive, outer halo globular cluster (GC) M 75 (NGC 6864). This unique system shows a very extended trimodal horizontal branch (HB), but no other clues for multiple populations have…
HD\,139614 is known to be a $\sim$14-Myr-old, possibly pre-main-sequence star in the Sco-Cen OB association in the Upper Centaurus-Lupus subgroup, with a slightly warped circumstellar disc containing ring structures hinting at one or more…
We use Multiple Mirror Telescope (MMT) spectrophotometry and Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra and Wide Field and Planetary Camera 2 (WFPC2) V and I images to study the properties and evolutionary status…
A search for lithium is performed on seven metal poor dwarfs with metallicities ranging from [Fe/H]=-1.5 down to [Fe/H]=-3.0 but showing disk-like kinematics. These stars belong to the metal poor tail of the Galactic thick disk and they may…
We have performed a differential, line-by-line, chemical abundance analysis, ultimately relative to the Sun, of nine very metal-poor main sequence halo stars, near [Fe/H]=$-$2 dex. Our abundances range from…
We report on a dedicated effort to identify and study metal-poor stars strongly enhanced in r-process elements ([r/Fe] > 1 dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). Moderate-resolution (~2A)…
We present the results of analysis of ``snapshot'' spectra of 253 metal-poor halo stars -3.8 < [Fe/H] < -1.5 obtained in the HERES survey. The spectra are analysed using an automated line profile analysis method based on the Spectroscopy…
We present the first detailed chemical abundances for seven GD-1 stream stars from Subaru/HDS spectroscopy. Atmospheric parameters were derived via color calibrations ($T\rm_{eff}$) and iterative spectroscopic analysis. LTE abundances for…